Deltiology (from Greek δελτίον, deltion, diminuitive of δέλτος, deltos, "tablet, letter"; and -λογία, -logia) is the study and collection of postcards. Compared to philately, the iden- tification of a postcard's place and time of production can often be an impossible task because postcards, unlike stamps, are produced in a decentralised, unregulated manner. For this reason, some collectors choose to limit their acquisitions to cards by specific artists and publishers, or by time and location.

Győr [Győr (Hungarian), Raab (German), Ráb (older Czech, older Slovak), Dyor - Дьёр (Russian)] is the most important city of northwest Hungary, the capital of Győr-Moson-Sopron county and lies on one of the important roads of Central Europe, halfway between Budapest and Vienna. The city is the sixth largest in Hungary and one of the seven main regional centres of the country.